Fertilizer Made From Urine Could Enable Space Agriculture

Manuring with man urine: researchers from Japan electrochemically create ammonia from urine to grow plants in space.
Credit: Freepik

Researchers at Tokyo University of Science devise a new electrochemical technology to manufacture ammonia-based fertilizer from urea.

From the perspective of future societies, in extremely closed environments such as a space station, self-sufficiency in food cultivation and waste management is critical. However, the technology to achieve this is still lacking. In a new study, scientists from Japan shed light on their most recent breakthrough: a cheap and efficient method to make liquid fertilizer (ammonia) from simplified artificial urine, serving an ideal dual purpose of growing food and treating waste.

In extreme environments, even the most ordinary tasks can seem like insurmountable challenges. Because of such difficulties, humanity has, for the most part, settled on grounds that were favorable for harvesting crops, herding cattle, and building shelters. But as we seek to expand the limits of human exploration, both on earth and in space, the people pioneering this search will undoubtedly face conditions that, for all intents and purposes, are not conducive to human habitation.

One of the foremost challenges facing any intended long-term settlement, be it in the Antarctic or on Mars (perhaps in the near future), is achieving some degree of autonomy, to enable isolated colonies to survive even in the event of a catastrophic failure in provisioning. And the key to achieving this autonomy is ensuring food sufficiency and self-sustenance. Unsurprisingly, therefore, space agricultural technology is one of the research topics currently being undertaken by the Research Center for Space Colony at Tokyo University of Science. The researchers here hope to spearhead the technological development for safe and sustainable space agriculture-with the aim of sustaining humans for a long time in an extremely closed environment such as a space station.

To this end, an innovative study was conducted by a team of Japanese researchers led by Junior Associate Professor Norihiro Suzuki from Tokyo University of Science-this study, published as a “Letter,” made the front cover of the prestigious New Journal of Chemistry of the Royal Society of Chemistry. In this study, Dr. Suzuki and his team aimed to address the problem of food production in closed environments, such as those in a space station.

Realizing that farmers have used animal waste as fertilizer for thousands of years, as a rich source of nitrogen, Dr. Suzuki and his team have been investigating the possibility of manufacturing it from urea (the main component of urine), to make a liquid fertilizer. This would also simultaneously address the problem of human waste treatment or management in space! As Dr. Suzuki explains, “This process is of interest from the perspective of making a useful product, i.e., ammonia, from a waste product, i.e., urine, using common equipment at atmospheric pressure and room temperature.”

The research team-which also includes Akihiro Okazaki, Kai Takagi, and Izumi Serizawa from ORC Manufacturing Co. Ltd., Japan-devised an “electrochemical” process to derive ammonium ions (commonly found in standard fertilizers) from an artificial urine sample. Their experimental setup was simple: on one side, there was a “reaction” cell, with a “boron-doped diamond” (BDD) electrode and a light-inducible catalyst or “photocatalyst” material made of titanium dioxide. On the other, there was a “counter” cell with a simple platinum electrode. As current is passed into the reaction cell, urea is oxidized, forming ammonium ions. Dr. Suzuki describes this breakthrough as follows, “I joined the ‘Space Agriteam’ involved in food production, and my research specialization is in physical chemistry; therefore, I came up with the idea of ‘electrochemically’ making a liquid fertilizer.”

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